Production of monopersulfuric acid



United States Patent 2,926,998 PRODUCTION or MONGPERSULFURIC ACID.

Alfred A. DAddieco, Grand Island, N.Y., and Stephen E. Stephanou, SantaAna, Calif assignors to E. I. du Pont de Nemours and Company,Wilmington, Dela, a corporation of Delaware No Drawing. Application May15, 1957 Serial No. 659,212

1 9 Claims. (0113 -166) This invention relates to the production ofmonopersulfuric acidby the reaction of hydrogen peroxide and oleum.

y This application is a continuation-in-part of copending not hithertobeen used in industry, possiblybecause no practical method has beenavailable for their manufacture, particularly from concentrated oieumand concentrated hydrogen peroxide. Concentrated solutions ofmonopersulfuric acid are useful and desirable for variouspurposesparticularly in the preparation of solid monopersulfateproducts.

It is an object of the invention to provide a prac-- tical and eflicientmethod for preparing concentrated monopersulfuric, acid solutions fromhydrogen peroxide and oleum as reactants. A specific object is a methodof'preparing monopersulfuric acid employing concentrated hydrogenperoxide and concentrated oleum as reactants in proportions found to becritical to the obtainment of eflicient conversions of the hydrogenperoxide to monopersulfuric acid. Still further objects will be apparentfrom the following description.

The objects of the invention are accomplished by mixing hydrogenperoxide of at least 50% strength (i.e., at least 50% H 0 by Weight) andoleum of 53 to 82% strength (Le. containing 53 to 82% free or dissolved80 by weight) in proportions Within a range found to be critical for theobtainment of efficient conversion of the hydrogen peroxide tomonopersulfuric acid. The mole ratio of oleum to hydrogen peroxideshould be within the rangell to 3.1, most preferably 1.3 to 2.7, molesof oleum per mole of hydrogen peroxide.

The term moles of oleum is used herein to mean the sum of the number ofmoles of free or dissolved S0 and the number of moles of sulfuric acidpresent in the amount of oleum employed.

Dilute (e.g., 30%) oleum has been proposed heretofore for reactions withhydrogen peroxide to produce dilute solutions of monopersulfuric acid.The present invention contemplates the use of oleum of 53 to 82%-strength, most preferably 57 to 74%. Oleums of such strengths are liquidat those temperatures suitable for carrying out the monopersulfuric acidreaction and can be readily, rapidly and efiiciently reacted withhydrogen peroxide in accordance with the invention. Oleurns of higher(e.g. 90%) and somewhat lower (e.g. strengths are solid at the desiredreaction temperatures and therefore diflicult to handle and cannot beefficiently mixed and reacted with hydrogen peroxide to obtain the2,926,998 Patented Mar. 1, 1960 desired product in good conversions. Atpreferred reaction temperatures not exceeding 15 C., oleum of, strengthsranging from 57m 74% should be used, since oleum of higher or lowerstrength is not liquid at 15 C. Similarly, at 10 C., oleum of 58 to 71%strength should be used. In any case, the oleum chosen for use should beof such a composition that it will be liquidat the reaction temperatureto be used.

it has been discovered that when employing oleum of 53 to 82% strengthand hydrogen peroxide of at least 50% strength as reactants, highconversions (at least 82%) of the active oxygen present in the reactionmixture to monopersulfuric acid requires the use of at least 1.1 but notmore than 3.1 moles of oleum (SO A-H per mole of H 0 The conversiondrops olf rapidly if the mole ratio of oleum to H 0 is either less than1.121 or. greater than 3.111. The preferred proportions range from 1.3to 2.7 moles of oleum per mole of H 0 in which range conversions upwardsof have been realized. Such high reactions efiiciencies are remarkablein view of the Well-known relative instability of perox-ygen compoundsand the high heats of reactions involved. when using concentratedreactants.

The hydrogen peroxide reactants should be at least 50% strength and mostpreferably will be of 65 to 90% strength, otherwise the productmonopersulfuric acid becomes unduly diluted. A further advantage inusing hydrogen peroxide of the above high strengths is that the heat ofreaction of sulfur trioxide with water and the heat of dilution arethereby minimized, which in turn reduces the amount of coolingnecessary.

Mixing of the oleum and peroxide reactants is pref-v point of the oleumused and about 15 C. (e.g., from about 0 to 15 C), at which temperaturesthe reaction to form monopersulfuric acid occurs rapidly with efiicientconversion to monopersulfuric acid. The most preferred temperaturesrange from about 3 to 10 C. Temperatures from 15 C. up to about 25 C.can be used, but with some sacrifice in active oxygen recoveries.Temperatures above about 25 C. are not recommended since they areconducive to poor efiiciencies due to hydrolysis of monopersulfuric acidand losses of active oxygen.

Mixing of the reactants should be efiected under efficient agitation andcooling. This can be accomplished, for example, by addingthe oleum at acontrolled rate to the hydrogen peroxide maintained under agitation andcooling. Alternatively, both reactants may be added simultaneously andseparately at rates controlled to provide the proper proportions of thereactants to an agitated cooled portion of a reaction mixture. Anothermethod is to flow the reactants separately and continuously at suitablerates into a-cooled pipeline type reactor wherein they are continuouslymixed by turbulent how and reacted as the mixture passes through thereactor.

The invention is illustrated by the following examples in which allparts and concentrations are parts and percentages by weight, unlessindicated to be otherwise.

EXAMPLE 1 To 34 parts (0.7 mole) of a cooled aqueous hydrogen peroxidesolution of 70% strength provided with an etlicient agitator, there wereadded 59.9 parts (0.7 mole) of 65% oleum during a period of 0.5 hourwhile main taining the resulting mixture at a temperature between 0-oxygen therein. This was accomplished by weighing 10 drops of themixture in a cooled weighing bottle, adding the sample to 40 ml. of cold1 N H 80 and analyzing for monopersulfuric acid (H 80 hydrogen peroxideand persulfuric acid (H S Q by essentially the method of Glen (Oester,Newer Methods of Volumetric Analysis, page 109 (1938)). The mixturewasfound to contain 66.8% H 80 5.5% H 0 and no H S O No loss of activeoxygen resulted but the monopersulfuric acid represented only 78% of theactive oxygen present.

The above procedure was repeated a number of times exceptthat the moleproportions of oleum (65%) to hydrogen peroxide (70%) were varied over aconsiderable range. Results obtained are tabulated below along withthose for Example 1.

Table of results Active Oxygen Recov- Reacted Mixture ContainedConversion 0%) Active xygen Recovered t0 H2505 (Percent) Moles ol perMole of H20:

cred (Percent) (Percent) H1805 H2 2 1 Active oxygen recovery somewhatlow because temperature control was inadequate.

A curve obtained by plotting the mole ratios of the second columnagainst the conversions of the last column of the above table shows thatmaximum conversion of recovered active oxygen to monopersulfuric acid isobtained at an oleum:H O mole ratio of about 1.721. It also shows thatconversions of at least 82% are realized at mole ratios ranging from1.1:1 to 3.1:1, but that conversion drops oif markedly when mole ratiosof less than 1.1:1 or greater than 3.1:1 are used. The preferred ratiosare in the range 1.3:1 to 2.7:1. When the reaction mixture is to be usedto prepare solid monopersulfate products, the most preferred mole ratiosof oleum:H O range from 1.321 to 1.8:1 since the resultingmonopersulfuric acid solutions contain the most suitable proportions ofmonopersulfuric acid and sulfuric acid for the recovery of stable solidmonopersulfate compositions.

The present method has been successfully practiced many times to obtaindirectly monopersulfuric acid solutions containing from around to 69%monopersulfuric acid by weight with upwards of 90% of the active oxygenpresent being in the form of the monopersulfuric acid.

We claim:

' 1. The method of producing monopersulfuric acid comprising mixingoleum containing from 53 to 82% dissolved S0 and hydrogen peroxide of atleast 50% strength at a temperature between the freezing point of saidoleum and about 25 C., in the proportion of from 1.1 to 3.1 moles ofsaid oleum per mole of said hydrogen peroxide.

2. The method of claim 1 employing from 1.3 to 2.7 moles of oleum permole of hydrogen peroxide.

3. The method of claim 1 employing 1.3 to 1.8 moles of oleum per mole ofhydrogen peroxide.

4. The method of producing monopersulfuric acid comprising mixing oleumcontaining from 57 to 74% dissolved S0 and hydrogen peroxide of tostrength at a temperature at which said oleum is liquid but not higherthan about 15 C., in the proportions of from 1.1 to 3.1 moles of saidoleum per mole of said hydrogen peroxide.

5. The method of claim 4 employing from 1.3 to 2.7 moles of oleum permole of hydrogen peroxide.

6. The method of claim 4 employing from 1.3 to 1.8 moles of oleum permole of hydrogen peroxide.

7. The method of producing monopersulfuric acid comprising mixing oleumcontaining about 65% dissolved S0 and hydrogen peroxide of 65 to 90%strength at a temperature between the melting point of said oleum and 15C., in the proportions of from 1.1 to 3.1 moles of said oleum per moleof said hydrogen peroxide.

8. The method of claim 7 employing from 1.3 to 2.7 moles of oleum permole of hydrogen peroxide.

9. The method of claim 7 employing from 1.3 to 1.8 moles of oleum permole of hydrogen peroxide.

Jones, W. N.: Inorganic Chemistry, Blakiston Co., 1947, page 419, lines3 to 7.

1. THE METHOD OF PRODUCING MONOPERSULFURIC ACID COMPRISING MIXING OLEUMCONTAINING FROM 53 TO 82% DISSOLVED SO3 AND HYDROGEN PEROXIDE OF ATLEAST 50% STRENGTH AT A TEMPERATURE BETWEEN THE FREEZING POINT OF SAIDOLEUM AND ABOUT 25* C., IN THE PROPORTION OF FROM 1.1 TO 3.1 MOLES OFSAID OLEUM PER MOLE OF SAID HYDROGEN PEROXIDE.